1. Field of the Invention
The present invention relates to a track maintenance machine comprising a machine frame having undercarriages for moving the machine frame in an operating direction along a track, and a track scanning unit adjustably connected to the machine frame and having flanged rollers for moving the track scanning unit along the track. This invention also relates to a method of monitoring a track position.
2. Description of the Prior Art
A machine and method of this type is known, for example, from EP 0 806 523 A1. The position of a track lifting device, which senses the track position, is measured relative to a machine frame of the track maintenance machine, and the machine frame position is determined by means of geodetically measured fixed points defining the absolute track position.
Furthermore, it is known from DE 41 02 871 C2 to measure the displacement of a track scanning unit, such as a measuring axle rolling on a track, relative to a machine frame of a track tamping machine running on the track.
Finally, EP 1 028 325 A2 discloses a method of measuring a track position by means of two independently moving measuring carriages positioned on the track at the end points of a track section to be measured.
It is the object of the invention to provide a machine and method of this general type, which enables the position of a track to be monitored quickly and with dependable accuracy.
According to one aspect of the present invention, this object is accomplished with a track maintenance machine of the first-described type, which comprises a satellite receiver connected to the machine frame, the satellite receiver having an antenna with an antenna center, a measuring device for monitoring the position of the antenna center relative to the track scanning unit with respect to the following parameters: transverse superelevation (xcex2), transverse displacement (d) perpendicular to a longitudinal extension of the machine frame and vertical distance (a), and a computer for a computed repositioning of the antenna center relative to a reference point of the track scanning unit.
Such a machine makes it possible to obtain an exact parallel guidance of the antenna center relative to the center axis of the track, despite a front arrangement of the satellite receiver on the machine frame, which assures an optimal reception of the extraterrestrial position signals by the satellite receiver.
According to another aspect of this invention, a method of monitoring a track position by scanning the track comprises the steps of determining the position of an antenna center of an antenna of a satellite receiver receiving extraterrestrial position signals relative to a reference point on a track scanning unit adjustably connected to a machine frame of a track maintenance machine and having flanged rollers for moving the machine frame in an operating direction along the track, the satellite receiver also being connected to the machine frame, and automatically recording the absolute track position coordinates in the range of the track scanning unit by determining the coordinate position of the antenna center by means of the position signals.